Packaging laminate and packaging container

ABSTRACT

The disclosure relates to a packaging laminate ( 10 ) for a packaging container for a food product intended to be frozen, comprising a core layer ( 12 ) and outer, liquid-tight layers ( 14, 16 ), the packaging laminate ( 10 ) including an outer, thermosealable layer ( 14, 14   a ) which, at least in selected part regions thereof displays a brittle point between −25° C. and +20° C. The invention also relates to a packaging container ( 30 ) for a food product intended to be frozen, which is formed from the packaging laminate according to the present invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/494,257filed May 4, 2004, the contents of which are incorporated herein byreference, which was the National Stage filing under 35 U.S.C. §371 ofPCT/SE02/02035 (published in English as WO 03/039865 A1 on May 15,2003), which in turn claims priority to Swedish Application No.0103627-6, filed Nov. 9, 2001.

TECHNICAL FIELD

The present invention relates to a packaging laminate for a packagingcontainer for a food product which is intended to be frozen, comprisinga core layer and outer, liquid-tight layers. The present invention alsorelates to the packaging container which is formed from the packaginglaminate. The present invention has primarily been developed to beutilised for the packing of a food product which is substantiallyliquiform in the unfrozen state, but is substantially solid in thefrozen state, the food product preferably consisting of water ice orsherbet.

BACKGROUND ART AND PROBLEMS

For packaging containers intended for food products which are stored andtransported in substantially liquid state, there is generally a problemin providing the packaging container with an opening arrangement which,on the one hand, withstands rough handling during storage and transportwithout beginning to leak and, on the other hand, is easy to open forthe end user, preferably without the need for utensils in the form, forexample, of a pair of scissors. Moreover, the opening arrangement shouldsatisfy a number of criteria related to manufacture, such as low cost,few manufacturing steps and few machine components required in themanufacturing process.

One of the simplest, and thereby most economical opening arrangementsconsists of a perforation. This is the opening arrangement which hashitherto been utilised in a classic tetrahedral shaped portion packageof the type which carries the registered trademark Tetra Classic®, whenthis package contains water ice or sherbet. The tetrahedral shapedpackage tapers cuneiformly towards a seal of the “praying” type, i.e. aseal in which the outer sealing layer of the packaging laminate (facingtowards the product) directly abuts against and is sealed against itselfin such a manner that the free edges of the packaging laminate face outin a “fin” from the package like two hands joined in prayer. Inside theseal, seen in a direction from the projecting “fin”, this packagedisplays a perforation on both sides of the package, the perforationbeing as long, or almost as long, as the seal.

This package, for water ice or sherbet, can be stored and transportedwith its contents in the unfrozen state, but only opened and consumedonce it and its contents have been frozen. The package type is excellentfor this purpose, but one problem resides in that the packagingmaterial, on transport and storage, tends to fold in the perforationimmediately inside the seal, there then being a risk of leakage, inparticular in the edges of the fin at the fold-over of the laminate.Attempts to solve this problem have been made in that the perforationhas not been permitted to extend right out into the ends/edges of thefin—which has, however, resulted in the package becoming extremelydifficult to open without some form of utensil.

OUTLINE OF THE INVENTION

The present invention has for its object to disclose a packaginglaminate for a packaging container for a food product which is intendedto be frozen, the packaging laminate and packaging container obviatingor at least reducing the above-described problems.

The present invention particularly has for its object to disclose apackaging laminate and a packaging container for a food product which isintended to be frozen, the packaging laminate and the packagingcontainer respectively making for and displaying a seal and/or openingarrangement which is strong and durable when the food product is “weak”,i.e. unfrozen, and which is weak and easily opened when the food productis “strong”, i.e. frozen and consequently hard.

The present invention further has for its object specifically todisclose a packaging container for a food product which is intended tobe frozen, the packaging container being capable of being opened in thefrozen state without the employment of utensils, preferably direct inthe seal without perforation.

These and other objects will be attained according to the presentinvention by means of a packaging laminate as disclosed in appendedClaim 1, as well as a packaging container as disclosed in appended Claim12.

The principle according to the present invention is thus based on theconcept that the packaging laminate, and thereby the packagingcontainer, is provided with an outer thermosealable layer which, atleast in selected part regions thereof, displays a brittle point between−25° C. and +20° C. These possible part regions constitute the partregions where seals are provided or are to be disposed, but it isnaturally also conceivable, and often most preferable, that all orsubstantially all of the one surface of the packaging laminate isprovided with the above-mentioned outer thermosealable layer whichdisplays a brittle point between −25° C. and +20° C.

It is preferred that this brittle point is lowest −20° C., preferablylowest −15° C., and even more preferably lowest −10° C., but highest+17° C., preferably highest +15° C. and even more preferably highest+12° C.

However, in cold storage and/or transport, it is appropriate that thisbrittle point be lowest −20° C., preferably lowest −15° C., and evenmore preferably lowest −10° C., but highest +8° C., preferably highest+4° C. and even more preferably +2° C.

Thanks to the material selection in this outer, thermosealable layerwhich faces towards the interior of the packaging container, there canbe realised a seal which is tough and strong and thereby withstandsstresses when the temperature lies above the brittle point, as intransport and storage at around room temperature in the unfrozen state.At a temperature below the brittle point, as when the packagingcontainer with its contents of water ice or the like has recently beenremoved from a freezer, the seal is thereby brittle, weak andconsequently easy to open without utensils and, in the preferred case,even without perforation or other specifically provided openingarrangement. In this preferred case, a sharp edge of the frozen,cuneiform food product is quite simply pushed straight through the sealwhich is weak because of the low temperature and ruptures it.

One advantage in this context is also that the packaging container isnot normally exposed to loading or stresses on storage when it is in thefrozen state, i.e. when the seal is weak, and even if it were to beexposed to loading stresses, these would—because of the frozen and hardcontents—not be concentrated to the seal in the same manner as when thecontents are in liquid form.

In addition to the fact that the packaging container will be easy toopen in the frozen state (in particular for children), other advantagesreside in the fact that the packaging container is leak-proof ontransport and storage in the unfrozen state. Moreover, no loose partsare formed when the packaging container is opened, which otherwisebecome litter and are often not recycled. Further, the preferred casedoes not call for the employment of machine equipment for realisingperforation, which also reduces the number of manufacturing steps andhence costs.

DETAILED ACCOUNT OF THE INVENTION AND BRIEF DESCRIPTION OF THEACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with reference to the accompanying Drawings, in which:

FIG. 1 shows one preferred packaging laminate according to the presentinvention, seen in cross section; and

FIG. 2 shows one preferred packaging container according to the presentinvention, seen in perspective.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a preferred packaging laminate 10 according to the presentinvention. This comprises a core layer 12 of a polymer material orrather of paper or paperboard. The core layer 12 is the individuallythickest layer in the laminate 10 and also the layer which makes thegreatest contribution to the mechanical properties of the laminate, suchas flexural rigidity etc. On the one outer side of the laminate 10, theside being intended to face in towards the interior of the package andthereby towards the food product, there is disposed a thermosealablelayer 14 according to the present invention, which at least in selectedpart regions thereof, displays a brittle point between −25° C. and +20°C. The layer 14 suitably has a layer thickness of 2-50 μm.

On the opposite side of this outer thermosealable layer 14, the laminatedisplays a second outer thermosealable layer 16 which preferablyconsists of polyethylene or of a thermosealable layer which at least inselected part regions thereof, displays a brittle point between −25° C.and +20° C.

The two layers 14 and 16 also impart liquid-tightness to the packaginglaminate 10.

Between the outer, thermosealable layer 14 and the core layer 12according to the present invention, there is disposed a thin barrierlayer 18, preferably a gas barrier layer, and even more preferably anoxygen gas barrier layer. In the illustrated case, the barrier layerconsists of an aluminium foil (Alifoil).

Between the core layer 12 and the barrier layer 18, use is suitably madeof an interjacent polymer lamination layer, glue or other adhesive 20.In the illustrated embodiment, this lamination layer 20 consists ofpolyethylene or of a polymer material which displays a brittle pointbetween −25° C. and +20° C.

Prom the practical viewpoint relating to production engineering, it maybe preferred that all polymer layers in the laminate consist of the sametype of material with a brittle point between −25° C. and +20° C. as theouter, thermosealable layer 14 according to the present invention. Onthe other hand, from the economical point of view, it may be preferredthat only an outermost layer 14 a of the outer, thermosealable layer 14consists of a material with a brittle point between −25° C. and +20° C.In such an event, this outermost layer 14 a suitably displays a materialthickness of 2-15 μm, preferably 2-10 μm, and is preferably disposedtogether with an inner thermosealable layer 14 b which also constitutespart of the outer thermosealable layer 14. This inner thermosealablelayer 14 b is preferably formed from polyethylene. The twothermosealable layers 14 a and 14 b have most preferably been providedby co-extrusion and together display a layer thickness of 15-50 μm,preferably 5-45 μm.

It may also be the case that the outer, thermosealable layer 14according to the present invention include at least two preferablyco-extruded part layers 14 a, 14 b, which are formed from the samematerial and, at least in selected part regions, display theabove-mentioned brittle point according to the invention. Also in thiscase, the part layer 14 a displays a layer thickness of 2-15 μm,preferably 2-10 μm, while the layers 14 a and 14 b together display alayer thickness of 15-50 μm, preferably 25-45 μm.

Regardless of whether the thermosealable layer 14 according to thepresent invention consists of a thin outer layer 14 a of the typeaccording to the invention provided together with an innerthermosealable layer 14 b of conventional type, or whether it consistsof one layer 14 or at least two layers 14 a, 14 b of the type accordingto the present invention, the brittleness is created at low temperaturein that the layer/layers 14 a; 14; 14 a, 14 b of the type according tothe present invention include a polymer material which displays thisbrittle point. According to one aspect of the present invention, thispolymer material includes at least one brittle point-lowering polymer,which preferably consists of a polyolefin and most preferably ofpolypropylene. It is preferred that this polymer material also includepolyethylene, the polyethylene and brittle point-lowering polymerideally existing in a mechanical or physical mixture, most preferably ascopolymer. Suitably, the above-mentioned brittle point-lowering polymeris present in a quantity of up to 40 weight %, preferably 1-30 weight %,and even more preferably at least 10 weight % in the above-mentionedpolymer material.

According to another aspect of the present invention, theabove-mentioned polymer material consists of a polymer material which,after treatment, for example heating (possibly in the form of zoneheating), is caused to permanently display the above-mentioned brittlepoint.

FIG. 2 shows one preferred aseptic packaging container 30 according tothe invention. This typically displays a volume of at most 200 ml, atleast in the case when it is intended for water ice or sherbet and istetrahedral in shape. Packaging containers of this type are producedsuch that a web of the packaging laminate is first reformed into a tubeby both longitudinal edges of the web being united to one another in aliquid-tight overlap joint 22 with the sealing layer 14 placed on thatside of the core layer which is turned to face inwards in the tube. Thetube is aseptically filled with the contemplated contents, e.g. waterice or sherbet in the unfrozen state, and is divided by repeatedtransverse thermal seals 24, 26 alternatingly 90° transversely inrelation to one another, into individual tetrahedral packaging units 30which are separated from one another by incisions in the transversesealing zones. The transverse sealing zones 24, 26 will thereby be ofthe “praying” type, the free edges of the fin 21 facing out from thepackaging container. At the same time, the packaging container taperscuneiformly towards these transverse seals 24, 26, with the result thata frozen food product within the packaging container 30 will display asharp edge which can be pushed through the seal 24 when the package isto be opened. The seal 24 in the opening end of the package preferablydisplays an active sealing width of 0.3-5 mm, preferably 0.5-3.5 mm.Possibly blocked sealing, i.e. incompletely fused sealing, outside theactive sealing width is not counted in the active sealing width.

In the fin 21, there may be provided, immediately inside the seal 24,according to a non-preferred embodiment of the present invention, aperforation 28 which is as long as the seal 24 or possibly somewhatshorter (in which event the perforation is possibly absent at the edgesof the fin 21, i.e. the folded-over short ends of the packaginglaminate). Also in this case, i.e. the case when the perforation 28 isprovided, opening is facilitated by the brittle point of the polymermaterial. In this case, it is preferred that all polymer layers in thepackaging laminate consist of layers having a brittle point according tothe present invention. In the embodiment where the material for theouter, thermosealable layer 14 consists of a polymer material which,after treatment, is caused to permanently display the above-mentionedbrittle point, this treatment, for example in the form of zone heating,is suitably put into effect only in the region of the perforation 28, inother words suitably not at the thermoseal 24, 26 proper.

At the inner longitudinal edge of the fin 21, there may be provided acrease line 32 immediately inside the perforation 28 and whose purposeis to constitute a fold indication which prevents the packaging laminatefrom being folded in the perforation 28 during transport and storage.

On the inside of the longitudinal joint 22, the packaging container maybe provided with a sealing strip (not shown) which is preferably formedfrom the same material as the outer, thermosealable layer 14. Thissealing strip has for its purpose to protect the free, cut edges of thepackaging laminate against moisture and liquid.

The present invention is not restricted to the above-describedembodiments, but may be varied without departing from the scope of theappended Claims. For example, it should be perceived that whenpolyethylene is mentioned, this polyethylene may consist of anypolyethylene whatever suitable to the purpose, which may, for example bepolymerised using so-called free radical technology: low densitypolyethylene (LDPE); or using catalyst technology: high densitypolyethylene (HDPE), medium density polyethylene (MDPE), linear lowdensity polyethylene (LLDPE), very low density polyethylene (VLDPE),ultralow density polyethylene (ULDPE), or metallocene/single sitecatalyst PE (mPE). It should also be perceived that the presentinvention may also be utilised in connection with packaging containersof other configuration than that shown here, and with other types ofopening arrangements which are based on the concept that a seal or asealing layer is to be ruptured.

1. A packaging container for a food product intended to be frozen,formed from a packaging laminate comprising a core layer and outer,liquid-tight layers, wherein the packaging laminate displays an outer,thermosealable layer which, at least in selected part regions thereof,displays a brittle point between −25° C. and +20° C., wherein saidouter, thermosealable layer includes a polymer material which displayssaid brittle point, the polymer material including at least one brittlepoint-lowering polymer consisting of polypropylene, and wherein thepolymer material also includes polyethylene, wherein the packagingcontainer is formed with a sealing fin, a free edge of the sealing finfaces out from the packaging container, and the packaging containertapers cuneiformly towards the sealing fin.
 2. The packaging containeras claimed in claim 1, wherein said brittle point is −20° C. to +17° C.3. The packaging container as claimed in claim 1, wherein said brittlepoint is −20° C. to +8° C.
 4. The packaging container as claimed inclaim 1, wherein said polyethylene and said brittle point-loweringpolymer are present as a copolymer.
 5. The packaging container asclaimed in claim 4, wherein said brittle point-lowering polymer ispresent in a quantity of up to 40 weight % in said polymer material. 6.The packaging container as claimed in claim 1, wherein said outer,thermosealable layer displays a layer thickness of 2-50 μm.
 7. Thepackaging container as claimed in claim 6, wherein said outer,thermosealable layer displays a layer thickness of 2-15 μm.
 8. Thepackaging container as claimed in claim 1, wherein said outer,thermosealable layer displays a layer thickness of 15-50 μm.
 9. Thepackaging container as claimed in claim 1, wherein said core layerconsists of polymer material, paper or paperboard, and wherein a barrierlayer is disposed between the core layer and one of the outer,liquid-tight layers.
 10. The packaging container as claimed in claim 1,wherein on its opposite side to said outer, thermosealable layer, itdisplays a second outer, thermosealable layer which consists ofpolyethylene or of a thermosealable layer which at least in selectedpart regions thereof displays said brittle point.
 11. The packagingcontainer as claimed in claim 1, wherein all polymer layers included inthe packaging laminate, at least in selected part regions thereof,display said brittle point.
 12. The packaging container as claimed inclaim 1, wherein said food product is substantially liquiform in theunfrozen state, but substantially solid in the frozen state.
 13. Thepackaging container as claimed in claim 1, wherein it displays a seal inwhich said outer, thermosealable layer directly abuts and is sealed toitself in a so-called praying seal.
 14. The packaging container asclaimed in claim 13, wherein said seal displays an active sealing widthof 0.3-5 mm.
 15. The packaging container as claimed in claim 13, whereinthe container is tetrahedral in configuration.
 16. The packagingcontainer as claimed in claim 2, wherein said brittle point is −15° C.to +15° C.
 17. The packaging container as claimed in claim 2, whereinsaid brittle point is −10° C. to +12° C.
 18. The packaging container asclaimed in claim 3, wherein said brittle point is −15° C. to +4° C. 19.The packaging container as claimed in claim 3, wherein said brittlepoint is −10° C. to +2° C.
 20. The packaging container as claimed inclaim 5, wherein said brittle point-lowering polymer is present in aquantity of 1-30 weight % in said polymer material.
 21. The packagingcontainer as claimed in claim 5, wherein said brittle point-loweringpolymer is present in a quantity of 10-30 weight % in said polymermaterial.
 22. The packaging container as claimed in claim 7, whereinsaid outer, thermosealable layer displays a layer thickness of 2-10 μm.23. The packaging container as claimed in claim 7, wherein said outer,thermosealable layer is provided together with an inner, thermosealablelayer by coextrusion.
 24. The packaging container as claimed in claim 8,wherein said outer, thermosealable layer displays a layer thickness of25-40 μm.
 25. The packaging container as claimed in claim 8, wherein theouter, thermosealable layer includes at least two coextruded part layerswhich, at least in said selected part regions thereof, displays saidbrittle point.
 26. The packaging container as claimed in claim 9,wherein the barrier layer consists of aluminum.
 27. The packagingcontainer as claimed in claim 14, wherein said seal displays an activesealing width of 0.5-3.5 mm.